Exciting news! We're transitioning to the Statewide California Earthquake Center. Our new website is under construction, but we'll continue using this website for SCEC business in the meantime. We're also archiving the Southern Center site to preserve its rich history. A new and improved platform is coming soon!

Spectral-Element Moment Tensor Inversions for Earthquakes in Southern California

Qinya Liu, Jascha Polet, Dimitri Komatitsch, & Jeroen Tromp

Published October 2004, SCEC Contribution #772

We have developed and implemented an automated moment tensor inversion procedure to determine source parameters for southern California earthquakes. The method is based upon spectral-element simulations of regional seismic wave propagation in an integrated 3D southern California velocity model. Sensitivity to source parameters is determined by numerically calculating the Fr├ęchet derivatives required for the moment tensor inversion. We minimize a waveform misfit function, and allow limited time shifts between data and corresponding synthetics to accommodate additional 3D heterogeneity not included in our model. The technique is applied to three recent southern California earthquakes: the 9 September 2001, ML 4.2 Hollywood event, the 22 February 2003, ML 5.4 Big Bear event, and the 14 December 2001, ML 4.0 Diamond Bar event. Using about half of the available three-component data at periods of 6 sec and longer, we obtain focal mechanisms, depths, and moment magnitudes that are generally in good agreement with estimates based upon traditional body-wave and surface-wave inversions.

Liu, Q., Polet, J., Komatitsch, D., & Tromp, J. (2004). Spectral-Element Moment Tensor Inversions for Earthquakes in Southern California. Bulletin of the Seismological Society of America, 94(5), 1748-1761. doi: 10.1785/012004038.